Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease, predominantly of prematurely born infants, characterized in its severest form by extensive hemorrhagic inflammatory necrosis of the distal ileum and proximal colon. NEC affects thousands of newborns in the U.S.A. every year with death occurring in 10-50% of affected individuals. As more premature infants are born in this country each year, the effects of this disease are likely to contribute to greater morbidity and mortality. The pathophysiology of this disease remains poorly understood; however prematurity, enteral feeding, intestinal hypoxia-ischemia, and bacterial colonization are considered major risk factors. Currently, no predictive diagnostic tests are available at the subclinical phase of this disease. A better understanding of the mechanisms involved in the development of NEC and elucidation of early pathological changes in tissues at the molecular level will help to improve therapy and could lead to prevention of this disease. Currently, the best animal model used to study NEC is the neonatal rat model. In this model, NEC is developed by feeding newborn rats milk-based formula and then exposing them to hypoxia and cold stress. The major advantage of the neonatal rat NEC model is that many clinical and pathological changes are similar to those found in humans. In addition, the major risk factors for human NEC (intestinal immaturity, enteral formula feeding, and hypoxia/ischemia) are essential factors to develop disease in the rat model. The major disadvantage of this model is the lack of knockout or genetically modified rat strains with which to investigate mechanisms of disease development and pathology. Currently, mechanistic evaluations in the rat model require inhibition of potential disease contributors with specific antibodies or specific chemical inhibitors. The paucity of congenic, knockout or spontaneous mutant rat strains has severely hampered research into this disease. Thus, the ability to utilize a neonatal mouse model of NEC would exponentially increase the ability to investigate disease pathogenesis. We propose to develop and characterize a neonatal mouse model of NEC. We will attempt to induce NEC in newborn mouse pups using the protocol currently utilized in our laboratory to develop NEC in neonatal rats - enteral hand feeding with cow-milk based formula coupled with twice daily exposure to asphyxia and cold stress. We will determine (I) the best strain(s) and conditions conducive to disease development, and (2) characterize disease development in these strains using histologic, biochemical and molecular means.